1. Field of Invention The present invention relates to devices for measuring optical powers of lenses and methods of measuring optical powers of lenses.
2. Discussion of Related Art
All references cited anywhere in this specification, including this background section, are hereby incorporated by reference herein.
Since the invention and first implantation of an intraocular lens (IOL) back in 1949 (Apple, D. & Sims, J. Surv. Opthalmol. 40, 279-292 (1996)), the development and use of IOL's has revolutionized refractive cataract surgery. An estimated 20.5 million Americans over age 40 have cataracts in at least one eye and more than 1.5 million cataract surgeries are performed per year. (See, National Eye Institute, Archive of Opthalmology, accessed Jun. 22, 2005, http://www.nei.nih.gov/eyedata/pbd6.asp.) The focal length (or dioptric power) is a fundamental parameter whose precise measurement is of critical importance for characterizing and evaluating the effectiveness and safety of a single focusing optical element or systems such as various positive and negative IOL's, contact lenses, eyeglasses, conventional lenses, objectives, and mirrors. Because of the complexity in accurately locating the principal focal planes that usually lie within the focusing element, various indirect methods for focal length measurement are conventionally used such as image magnification, autocollimation, nodal slide, Bessel's method, moiré deflectometry, and Talbot interferometry. (See, W. Smith, Modern Optical Engineering (McGraw-Hill, New York, 1990); Nakano, Y. & Murata, K. Applied Optics 24, 3162-3166 (1985); Su, D. & Chang, C. Optics Communications 78, 118-122 (1990); Keren, E. et al. Applied Optics 27, 1383-1365 (1988); Tognetto, D. et al, Investigative Opthalmology and Visual Science 45, 2682-2688 (2004); and Norrby, N. et al. Journal of Cataract and Refractive Surgery 22, 983-987 (1996).) The effectiveness of most of these methods is often limited in regards to high accuracy, dynamic range over which measurements can be performed (for both positive and negative dioptric powers), spatial sample alignment and subjectively image observation. Recently (Ilev, I. Optics Letters 20, 527-529 (1995); Ilev, I. et al. Applied Optics 35, 716-718 (1996); and Ilev, I. et al. Optical Review 4, 58-60 (1997)), we have demonstrated a fiber-optic based back-reflectance technique for testing focusing optical elements with relatively large numerical apertures and short positive focal lengths. This approach is compatible with high-resolution confocal laser microscopy and the combined fiber-optic confocal imaging systems offer advantages in terms of high spatial resolution, flexibility, miniaturization and scanning potential. (See, B. Flusberg et al. Nature Methods 2, 941-950 (2005).) For at least these and other reasons there is a need for improved devices and methods of measuring optical powers of lenses.